The invention relates to photolithography, and more particularly, to a method for fabricating patterns using a photomask.
A semiconductor device, for example, a Dynamic Random Access Memory (DRAM) device, is made up of numerous fine patterns formed using a lithography process. In the lithography process, a resist layer is coated on a target layer to be patterned, and an exposure process and a development process are performed on the resist layer to form a resist layer pattern, which exposes a portion of the target layer. An etching process using the resist layer pattern as a mask is performed to remove the exposed portion of the target layer, to form the pattern. The resist layer pattern is then removed. As a design rule of the patterns formed on a semiconductor substrate is decreased with an increase in integration degree of the semiconductor device, a Critical Dimension (CD) of the pattern is also decreased. Therefore, a photomask having a fine pattern is required to form a highly integrated circuit using a lithography process. A binary mask has been used as the photomask. The binary mask includes a light shielding layer pattern formed on a transparent substrate. Transmitted light can be made incident on a wafer after passing through the substrate alone. In order to fabricate finer patterns on the wafer, a half-tone phase shift mask using a phase shift material having a transmittance of several percent has also been suggested and employed.
In the application of the lithography technology using this photomask, design data which contains a layout for the pattern is required to fabricate one pattern. Design data is information made with design layout data. For example, another completed design layout data for a hole-type pattern is required to fabricate or modify a CD and a shape of a hole-type pattern. Therefore, if modification or change of the pattern is required, it is necessary to establish new design layout data. Since this additional design takes much time to develop, it can lead to a delay of the development of the photomask. Consequently, increased time and effort are required to obtain the finally completed mask.